Flux for soft soldering



Patented 16, 193 01 UNITEDSTATES-PATENT OFFICE f nowaan a mean), or near cmcaeo, mnnma, assrenoa 'ro ran enasszenm onmrrcan conranr, or canvnnann, one, a conroaarron or DELAWARE m1 ron sor'r sonnname Io Drawing.

Zinc chloride is perhapsflthe most common material used in the preparation of fluxes for soft soldering. It has the great disadvantage of being corrosive and if the soldered metal pieces are not thoroughly cleaned after the work is done traces of zinc chloride lefton the solder will gradually corrode the metal.

Rosin, or colophony is the base-of, other types of fluxes which are extensively used.

ey are commonl applied either in the form of pastes or a coholic solutions. They are not corrosive to the same extent as zinc chloride, but are notquite as eflicient.

The present invention has for one of its purposes the use in soldering of a practically non-corrosive and eflicient flux.

I have found that organic amine soaps have the properties requlred of an eflicient soldering flux and my invention relates to soldering processes where a flux comprising an amine soap is used. 7

Free fatty acids and of course, rosin acids, have as a general class, to a certain-extent the properties of wetting metals and dissolvin the oxide films present on metal pieces to e soldered, whereby theyallow the solder to wet and spread and thereby unite with the metal pieces; they are, however, diflicultly soluble in water and can therefore only be used'in solutions ofi organic solvents, whereby their cost as fluxes becomes rohibitive. Organic amines, on the other han have only I in individual and exceptional cases been addition are found to possess fluxing properties. By chemically combining the two substances new chemical compounds are produced in which the fluxing properties of the base materials is greatly enhanced and which in airly soluble in water. Butylamine and the fattyacid of cocoanut oil have for instance, individually, very little, if any fluxing properties; when the two are combined to form the cocoanut oil but lamine soap a substance results which in e ciency as a soft soldering flux compares favorably in many instances with zinc chloride fluxes; Chemically, soaps are generally understood to be salts, or combinations of a fatty acid,

including the rosin acids, with a basic com-4 pound and the term organic amine soaps lppli'oation'flled December 26, 1928. Serial No. 416,753.

as used herein is meant to define soaps under 1 the general classification in which the basic compound 1s an organic amine. The organic amine soaps are easily and conveniently prepared by melting together a free fatty acid necessity, as in the case 0 rosin fluxes, for

using alcoholic solutions.

The following is a partial list of'organic amine soaps used as soldering fluxes according to my invention and which were found to be satisfactory and eificient:

Toluidine stearate; aniline-stearate; diphenylamine-stearate; beta-naphthylamine stearate; butylamine-stearate; p-aminophe uo'l-stearate; p-toluidine-stearate; tri-ethauolamine-stearate; beta-naphthylamine oleate; o-toluidine-oleate; anihne-olea'te; butylamine-oleate; tri-ethanolamine-oleate; soaps from aniline, o-toluidine, beta-naphthylamine, tri-ethanolamine, diphenylamine and the cocoanut oil fatty acid; di-ethylamineresinate, tri-ethanolamine-resinate.

While particularly .eiilcient on tin plate with the usual 50 tin-50 lead solder, my novel fluxes have also outstanding fluxing properties on other metals such as brass, co per, alvanized iron, which are common y united by soft soldering, and they can be used to advantage over zinc chloride, rosin or ammonium rosinate fluir'es on such various. metals.

It is, of course, very diflicult to compare numericall the efliciency of fluxes, but any one skills the art easily recognizes if a flux works well or is inoperative in soldering. An attempt has been made to demonstrate flux efliciency by making comparative tests under standard conditions, wherein a predetermined amount of solder is applied to a piece of metal without or with a flux and measuring the thickness of the solder after cooling. The thicker the solidified drop of solder is found, the less it has spread and the less has been the efliciency of the amine soap.

flux. Applying such a test to organic amine soap fluxes, I .found, for instance,- that on tin plate the height of the solder was from to that of the solder applied without flux and in no instance was a reduction of less than found.

The organic amine soaps can be, used as fluxes in exactly the same manner as previously known fluxes. They can be apphed as such or in aqueous solution or suspension, or if desired in alcoholic solutions. A 12% aqueous 'ethanolamine-oleate soap solution was for instance used as aflux in tin plate solderin and was found entirely satisfactory. he concentration of the flux or amount used depends upon the desired spread of the solder and can be varied as is well known by those skilled in the solderin art.

claim:

1. In a the step ,0 applying a soldering ux comprlsmg an organic amlne soalp.

2. In a rocess of soft so denn metals the step 0 applying a soldering ux comprising an aqueous solution of an organic 3. In a fprocess of soft solderirg metals the step 0 applying a soldering ux comprising an aqueous solution of an organic amine-fatty acid soap.

4. As a soldering flux'an organic amine soap.

5. As a soldering flux an organic aminefatty acid soap.

6. As a soldering flux an aqueous solution of an organic amine soap.

In testimony whereof, I afiix my signature.

HOWARD S. McQUAID.

Process of soft solderin metals 

